The statements in this section merely provide background information related to the present disclosure and cannot constitute prior art.
The use of composite materials is already familiar with a view to lightening a turbomachine, in particular for an aircraft. Such materials are used to produce blades and annular casings. The latter generally comprise an essentially fine wall, which permits a flow to be delimited and guided inside the turbomachine.
Such a composite wall generally comprises an organic matrix and a fibrous reinforcement that is densified by the matrix. The fibrous reinforcement can comprise a preform that is woven in a three-dimensional manner, and/or can comprise a stack of woven fibrous plies.
Such a casing is known from document US2012/0270006 A1. This document discloses a composite casing having a tubular wall produced from a composite material. The composite material exhibits a matrix and a stack of plies having fibers arranged in two perpendicular directions. The orientation of the plies is adapted depending on the thickness of the tubular wall, in such a way as to prioritize particular orientations of fibers at certain positions on the wall. This arrangement of fibers enables the mechanical resistance of the casing to be improved, in particular in the area of the annular mounting flange.
This approach optimizes the resistance of the composite casing. Its rigidity remains low, however, and it can become insufficient in the case of external compressor casings, since these casings are subjected to high loadings. In the event of the loss of a fan blade, the turbomachine exhibits major amplitudes of vibration, and certain of the rotor blades of the compressor can come into contact with the composite casing. The latter is then highly stressed. It should also be noted that the thermal loads and the humidity lower the mechanical resistance of the casing.